1. Field of the Invention
This invention relates to an electromagnetic actuator for a disc drive and more particularly to a magnetic core configuration which produces enhanced flux density and increased force.
2. Description of the Prior Art
A typical electromagnetic actuator for disc drive includes a fixed core having a working gap in which a magnetic flux field is produced by one or more permanent magnets. A carriage that supports a read/write head for cooperation with a magnetic data disc carries an electromagnetic coil and is arranged for operation within the working gap in the core. Application of current of proper magnitude and polarity to the coil produces a magnetic field which reacts with the magnetic field in the working gap to apply force to the carriage in a direction radially of the disc. Such force causes movement of the carriage and the read/write head. Rapid movement of the carriage and read/write head is desirable in order to minimize the time required to access data on a given portion of a disc. Greater force on the carriage reduces the time required for the carriage to be moved and greater flux density in the core working gap produces a greater force.
U.S. Pat. No. 4,305,105 discloses a linear actuator for a magnetic disc drive that has a plurality of iron fingers of arcuate shape which fit into correspondingly shaped slots on a movable bobbin. The bobbin has a voice coil which produces magnetic flux that cooperates with magnetic flux produced by permanent magnets associated with the fingers.
U.S. Pat. No. 4,287,445 discloses a high performance disc drive actuator having a hollow rectangular carriage and a fixed magnetic core that defines a channel shaped to receive the hollow rectangular carriage, there being a voice coil on the carriage and permanent magnets in the housing to produce a flux field within the channel.